Typically, a metal separator is applied to a fuel cell, the metal separator has channels for a reactant and cooling water, a pair of gas diffusion layers (GDL) 12 for facilitating the diffusion of the reactant, and a membrane electrode assembly (MEA) 11 in which a chemical reaction occurs and which is positioned between the pair of gas diffusion layers (GDLs) 12. In the metal separator, channel parts 41 in which the reaction gas flows in the same direction as a flow direction of the reaction gas and land parts 42 which are in contact with the GDLs 12 are repeatedly formed, and passages of an anode separator 30 and a cathode separator 20 are symmetrical to each other, such that a space between the anode separator 30 and the cathode separator 20 is used as a cooling passage, as shown in FIG. 1.
In addition, to maximize performance of the fuel cell, a channel pitch of the separators 20 and 30 may be required to be dense to improve surface pressure to the GDL 12 and MEA 11, and then, the GDL 12 may be able to have constant permeability over an entire reaction surface. However, reducing the channel pitch of the separators 20 and 30 may be limited due to a defect such as crack or spring-back occurring during manufacturing, and the other performance deterioration factors may occur due to such defects.
For example, diffusion of reaction gas and discharging properties of produced water may deteriorate. When the channel pitch is substantially large, stress may be concentrated on the land part 42 in which the separator and the GDL 12 contact each other, such that surface pressure may not be applied sufficiently uniformly. Therefore, a porous structure of the GDL 12 may be destroyed, such that permeability of the GDL 12 may deteriorate and diffusion of the reaction gas and a discharging property of produced water may deteriorate. Further, when stress is reduced in the channel part 41, the GDL 12 may permeate into the channel part 41 to deteriorate a fluidity of the reactant flow.
In addition, membrane damage may occur when the land part 42 in which the structure of the GDL 12 is destroyed, carbon fibers may permeate into a membrane thereby damaging the membrane. Moreover, non-uniformity of electrical conductivity may occur. In the channel part 41 in which the GDL 12 is exposed, the reaction gas may be smoothly supplied, to cause an active chemical reaction. However, when surface pressure between the GDL 12 and the MEA 11 is insufficient, a contact resistance may increase, thereby inhibiting movement of electrons generated by a reaction.
The matters described as the related art have been provided only for assisting in the understanding for the background of the present invention and should not be considered as corresponding to the related art known to those skilled in the art.